In certain applications, such as airplane cockpits, illuminated indicators are required for electrical switches to allow the operator to determine whether the switch is in an "on" or "off" state. Conventional switches have used incandescent lamps to provide such indicator lights. In large numbers, however, such incandescent lights produce a large quantity of heat which is inefficient an potentially unsafe in closed environments such as airplanes.
In the past it has been known to use fibre optic controls to control the functioning of electrical devices to provide a safer system for use in wet, hospital, explosive or other hazardous environments. For example see U.S. Pat. No. 3,999,074 which describes a fibre optic electric power control device, and U.S. Pat. No. 4,704,656 which discloses a fibre optic switch for controlling a wall receptacle. Such devices use the fibre optic switch to provide a light signal to a photo-electric device which in turn controls the electrical circuit. In this way the fibre optic control can be made remote from the electrical circuit. To date, however, none of these devices have provided fibre optic indicator illumination. Further, such devices have not incorporated the light guide into the casing of the unit itself for ease of manufacturing. Finally, none of the known prior devices have utilized a simple mechanical actuator to switch the light into and away from an output optical path.
The invention as claimed is intended to remedy these problems. It provides light director in a mechanical actuator to direct light into or away from an output optical path depending on the position of the actuator. Coupling between an optical input and output path or paths are provided by a fibre optic or lightguided control system incorporated at least partly in a mechanical actuator. The switched light is used to control electrical circuits and to control the incidence of switched light onto a light indicator. According to the invention there is provided a switch for switching a beam of light which includes a housing, an actuator reversibly moveable with respect to said housing between a first and second position, an input optical path, a first output optical path, and a light redirecting means. The light redirecting means directs light from the input path to the first output path and includes a prism positioned on the actuator which is movable to and from a first position in a direction such that reflecting faces the prism are tangent to its direction of movement. The prism directs light from the input path to the first output path when the actuator is in the first position.
The switch may include a second optical output path. The light redirecting means includes a pair of prisms positioned on the actuator and movable from a first reflecting position to a second reflecting position such that the prisms move in a direction in which their reflecting surfaces are tangent to the direction of movement. A first output prism of the pair of prisms when in the first reflecting position is positioned to reflect light from the input path to the first output path and a second output prism of the pair of prisms when in the second reflecting position is positioned to reflect light from the input path to the second output path.
The switch may also include an actuator having a prism and a plurality of optical output paths with the prism rotatable so as to direct light from the input optical path to each of the output optical paths depending on the position of the actuator.
One or more indicators which become illuminated in response to incident light may be employed to indicate switch position. The housing of the actuator may be transparent so as to obviate the need for light transmitting lines such as light guides or fibres to be installed in the actuator.
The advantages of the invention over conventional electrical control systems are less complexity, greater reliability, reduced heat generation and lower costs.